Can end

ABSTRACT

A can end having a countersink bead, an inclined chuck wall and a strong seam, resists distortion from its circular profile when subjected to thermal processing or when packaging carbonated beverages. This high hoop strength affects the manner in which the can end ultimately fails when placed under extreme abuse conditions, even if buckle pressure performance is within industry specified standards. The can end of the invention has control features introduced which control the failure mode whilst maintaining specified buckle pressure performance. In one embodiment, the control feature comprises expansion of the countersink bead to act as a trigger for local peaking, together with a groove in the chuck wall which prevents the peaking force from being concentrated at a single point which could result in leaking by the production of a pin hole.

This is a continuation of PCT/EP03/03716 filed Apr. 10, 2003, whichclaims priority to EPO Application Number 02252800.4 filed Apr. 22,2002.

BACKGROUND OF THE INVENTION

This invention relates to a can end and a method of manufacture of sucha can end. In particular, it relates to a can end which has improvedperformance characteristics.

Containers such as cans which are used for the packaging beverages, forexample, may contain a carbonated beverage which is at a higher thanatmospheric pressure. Can end design has been developed to withstandthis “positive” buckle pressure (sometimes also referred to as “peaking”pressure) up to defined minimum values (currently 90 psi for carbonatedsoft drinks) under normal operating conditions before failure. About 8to 10 psi above this value, failure of conventional can ends involvesloss of the circular profile and buckling of the end which, ultimately,leads to eversion of the end profile. Abuse conditions may also arisewhen a container is dropped or distorted, or when the product within thecontainer undergoes thermal processing.

One solution to the problem of loss of circular profile is provided bythe can end which is described in our U.S. Pat. No. 6,065,634. The canend shell (that is, the unseamed can end) of that patent includes aperipheral curl, a seaming panel, a chuck wall at an angle of between30° and 60°, a narrow anti-peaking bead and a centre panel. Duringseaming of the shell to the can body, the chuck wall is deformed at itsupper end by contact with an anvil portion of the seaming chuck. Theresulting profile provides a very strong double seam since the annulusformed by the seam has very high hoop strength and will resistdistortion from its circular profile when subjected to thermalprocessing or when packaging carbonated beverages.

Stiffness is also provided to the beverage can end by the anti-peakingor countersink bead. This is an outwardly concave bead comprising innerand outer walls, joined by a curved portion. In the '634 patent thisbead has walls which are substantially upright, although either may varyby up to +/−15°. This patent uses a small base radius (best fit) for thebead, typically 0.75 mm or less.

It is known from U.S. Pat. No. 6,089,072 that the width of theanti-peaking bead can be reduced by free drawing of the inner wall ofthe bead. This latter method avoids undue thinning of the bead as it isreworked. The resultant narrower bead optimises the stiffness of the canand, consequently, its resistance to buckling when attached to a canbody having high internal pressure in the can.

Can ends such as those described in the above patents have high hoopstrength and/or improved buckle performance such that they resistdeformation when subjected to high internal pressure. In particular, thebuckle pressure of the end of the '634 patent is well above the 90 psican making industry minimum standard.

Whilst high hoop strength is predominantly beneficial it will affect themanner in which the can end ultimately fails. In a conventional can end,the circular periphery of the can end will tend to distort and becomeoval under high internal pressure. If the circular shape of the seamedend is free to distort to an oval shape under high internal pressure, asis usual, then part of the anti-peaking bead will open out along an arcat one end of the long axis of the oval shape as the can end evertslocally.

However, in the can end of the '634 patent in particular, it has beenfound that the stiff annulus formed by the double seam resists suchdistortion. As a result, when subjected to severe abuse conditions,dropping during transport, mishandling by machinery, freezing etc, ithas been found that the resultant failure mode may lead to leakage ofcan contents. When distortion of the seam or anti-peaking bead isresisted by a strong seam and/or anti-peaking bead, failure can be byeversion of the bead at a single point rather than along an arc. Suchpoint eversion leads to pin hole leaks or even splitting of the can enddue to the localised fatiguing of the metal and extreme conditions mayeven be explosive.

SUMMARY OF THE INVENTION

This invention seeks to control the failure mode and to avoidcatastrophic failure and leaking, whilst still achieving buckle pressureperformance well above the industry stipulated pressure of 90 psi.

According to the present invention, there is provided a can end shellcomprising a centre panel, a countersink bead, an inclined chuck wallportion, and a seaming panel, and further including one or more controlfeatures, each feature extending around an arc of part of thecountersink bead and/or the chuck wall whereby the failure mode of thecan end, when seamed to a can body, is controlled, and in which the oreach control feature comprises one or more of: an expansion of thecountersink bead, a shelf in the outer wall of the countersink, anindentation in the chuck wall, and/or coining.

For the avoidance of doubt, it should be noted that the term “arc” asused herein is intended to include a 360° arc, i.e. a control feature orfeatures which extend around the whole circumference of the can endshell. Furthermore, it should be noted that the term “inclined” is notintended to be limiting and the inclined chuck wall may have one or moreparts, any of which may be linear or curved, for example.

A control feature, such as a selectively weakened region, may beintroduced onto the can end in a variety of different ways, all of whichare intended to limit or prevent the concentration of strain. Controlfeatures or weakenings may be achieved by increasing the radial positionof the outer wall of the countersink bead, a shelf in the countersinkbead, an indentation in the chuck wall, or coining. Numerous variationsare possible within the scope of the invention, including those set outbelow.

Usually, a shelf in the countersink bead will be in the outer wall ofthe bead, and may be at any position up that wall. Clearly when theshelf is at the lower end of the outer wall it effectively correspondsto an expansion in the bead radius. A shelf or groove may be provided onany part of a radial cross-section through the bead but as the innerwall diameter position is often used as a reference for machine handlingpurposes and the thickness of the base of the countersink should ideallynot be reduced, the outer wall is the preferred location.

Preferably, an indentation in the chuck wall should be made so that inthe seamed can end, the indentation is positioned approximately at theroot of the seam. In the end shell this means that the indentationshould be made about half way up the chuck wall or in the upper half ofthe chuck wall, depending on the type of seam. The indentation may bemade using radial and indent spacers to control the radial andpenetration depth of the tool.

In one embodiment, a control feature may extend over a single arc behindthe heel of the tab, centred on a diameter through the tab rivet andnose. Alternatively, there may be a pair of control features,symmetrically placed one on either side of the tab, and ideally centredat +/−90° or less from the heel (handle end) of the tab. In thisembodiment, the arc length may be anything up to 90° in order toencompass any “thin point” due to orientation relative to grainorientation.

A control feature may comprise a combination of different types ofcontrol features, usually over at least a portion of the same arc of thecan end such that, where the arcs are not fully circumferential, thedifferent types are centred on the same can end diameter. For example,there may be an expansion of the bead wall/radius and an indentation inthe chuck wall for the same or each control feature. In this example,the indentation in the chuck wall may extend over the same length of arcas the bead expansion, a longer or a shorter arc length, with thecentres of the arcs being on the same end diameter. In yet anotherembodiment, there may additionally be a shelf-type groove, as well asthe bead expansion and chuck wall indentation.

The countersink bead may have its base radius enlarged and thenincorporate a control feature comprising a shelf in its outer wall. Inone example, the arc length of the bead expansion (and, where present,the shelf) is less than the arc length of the chuck wall indentation,such that the bead expansion (and shelf) acts as a trigger for localpeaking.

Where the control feature comprises an indentation or coined region onthe chuck wall, this may extend either internally or externally, or acombination of these around the arc. For the purpose of thisdescription, it is the side of the can end to which a tab is fixed whichis referred to as “external” as this side will be external in thefinished can. Preferably, however, the indentation extends inwardly asotherwise it may be removed by the seaming tool during seaming.

In a further embodiment, the end shell may additionally include coiningof a shoulder between the inner wall of the countersink and the centrepanel over an arc or pair of arcs.

The control feature is preferably made in a conversion press but it maybe made in a shell press or even in a combination of the shell andconversion presses providing that orientation of the end is not anissue.

Whilst the terms “groove”, “indentation” and “indent” have been usedabove, it should be appreciated that these terms also encompass anyreshaping of the can end to form a control feature, including the use ofa point indent or series of indents and other variations of points andgrooves.

BRIEF DESCRIPTION OF THE FIGURES

Preferred embodiments of the invention will now be described, by way ofexample only, with reference to the drawings, in which:

FIG. 1 is a perspective view of a conventional beverage can end;

FIG. 2 is a plan view of another type of beverage can end;

FIG. 3 is a partial side section of the can end of FIG. 2, prior toseaming;

FIG. 4 is a partial side section of the can end of FIG. 2, after seamingto a can body; and

FIG. 5 is a sectioned perspective view of a seamed can end having twotypes of control features.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The can end of FIG. 1 is a conventional beverage end shell 1 comprisinga peripheral curl 2 which is connected to a centre panel 3 via a chuckwall 4 and anti-peaking reinforcing bead or countersink 5. The centrepanel has a score line 6 which defines an aperture for dispensingbeverage. A tab 7 is fixed to the centre panel 3 by a rivet 8, as isusual practice. Beads 9 are provided for stiffening the panel.

The can end of FIG. 1 when attached by seaming to a can body which isfilled with carbonated beverage, for example, is typically able towithstand an internal pressure of 98 psi before buckling, 8 psi abovethe required minimum buckle pressure of 90 psi. When the pressureapproaches and exceeds this value, the circular shape of the peripheryof the end will distort and become oval. Eventually the centre panelwill be forced outwardly so that the countersink “unravels” and flipsover an arc of its circumference. Whilst a can which is buckled in sucha manner is unlikely to be acceptable to a consumer, the can end itselfis still intact, the tab 7 is still accessible and there is nocompromise to the sealing of the container by such failure which couldresult in leaking of the contents.

It has been found by the present Applicants, however, that where acontainer has an end which is, by virtue of its design, substantiallystiffer and has greater hoop strength than that of FIG. 1, the bucklefailure mode differs from that described above. Such a can end is thatof the '634 patent, shown for reference in FIGS. 2 to 4. The can end 20is attached to a can body 21 by a double seam 22, as shown in FIG. 4.Inner portion 23 of the seam 22, which is substantially upright, isconnected to a countersink bead 25 by a chuck wall 24. The countersink,or anti-peaking bead 25 has inner and outer walls 26 and 27, the innerwall 26 depending from the centre panel 28 of the end.

Whilst the higher hoop strength exhibited by this can end is of greatimportance in maintaining the overall integrity of the container, themode in which the can fails under severe abuse conditions may beunacceptable and even, on occasion, catastrophic. Typical failure modesmay compromise the integrity of the can by pin hole(s) and/or splittingof the can end. In extreme cases, the centre panel 28 is pushedoutwardly by excessive internal pressure. As the panel moves outwardly,it pulls the inner wall 26 of the anti-peaking bead 25 with it. Theinner portion 23 of seam 22 is “peeled” away from the rest of the seamas the can end is forced out. The explosive nature of this so-called“peaking” failure results in the formation of a bird's beakconfiguration with a pin hole at the apex of the “beak” where the forceis concentrated in a single point at the base of the countersink 25.

The Applicants have discovered that by providing the can end with acontrol feature, a preferential “soft” peak is obtainable when the canend fails. Although this means that the can end may fail at a lowerbuckle pressure, the softer, less explosive nature of the peak resultsin a failure mode without pin hole or tearing. The introduction of acontrol feature thus controls the failure mode and avoids concentrationof the forces at a single point.

Control features in accordance with the invention can take a variety offorms including one or more of the following with reference to FIGS. 3and 4:

-   A. The radial position of the outer wall 27 of the countersink bead    may be increased;-   B. The chuck wall 24 may be coined or have indentations at or above    approximately the mid-point such that this control feature is at the    root of the seam 22 in the seamed can end (denoted as B′);-   C. Coining of the inner shoulder (C) of the countersink or of the    outer shoulder (C′);-   D. A shelf may be made in the outer wall 27 of the countersink bead.

When a type D region is at the lower part of the outer countersink wall,this may be equivalent to a type A control feature. Higher up the outerwall, a type D region takes the clear form of a shelf.

In a preliminary trial of the present invention, the shell of FIGS. 2 to4 was modified by a local groove in the outer wall of the countersink.This groove was ideally adjacent the handle of the tab so that anyfailure of the can end would be away from the score. Positioning eitherside of the tab or, indeed, at any position around the countersink wasalso considered possible. The groove was typically about 8 mm in arclength and was positioned approximately half way down the outer wall ofthe countersink bead, in the form of a shelf. Computer modelling hasshowed that the provision of such a groove resulted in a failure modesimilar to that of a conventional can end such as that of FIG. 1, withno leakage.

Modelling and bench testing has revealed that even better control of thefailure mode was achievable when a pair of grooves were made at the baseof the countersink outer wall. A variety of variables were modelled andthen bench tested as follows: depth of groove bottom of outer wall* gapbetween grooves 3 mm to 6 mm radial interference (depth of 0.2 mm to 0.4mm penetration into outer wall) orientation behind (handle end of) tab60° to tab left only 60° to tab right only 60° to tab left and right*This is equivalent to increasing the radial position of the countersink(anti-peaking) bead.

In bench testing of a small batch of cans using each of the abovecombinations, it was found that whilst the majority of cans leaked, theprovision of a control feature controlled the position of peaking to theindentation site and all leaks were located on the peaks rather than onthe tab rivet or score.

In spite of the fact that the cans of the initial trial still leaked onpeaking, the Application discovered that the incident of leakage wasgreatly reduced by a combination of types of control features which may,individually, exhibit unacceptable leaking on peaking. The followingexamples show how the failure mode can not only be focussed on aparticular site on the can end but also be controlled such that the canalso has acceptable buckle performance. In all of these further trials,cans were heated to 100° F. before carrying out the drop tests.

EXAMPLE 1

Can ends were modified in the conversion press by expanding thecountersink bead over a 60° arc at positions +/−90° of the tab heel.These ends were then seamed onto filled cans and dropped vertically, tabend down, onto a steel plate, the sheet steel being inclined at 30°.This extreme test is non-standard and tested the cans for severe abuseperformance. The tests used the Bruceton staircase analysis and resultsare set out in table 1, where P=standard peak and PS=peak and scoreburst.

All cans tested peaked at the control feature without splitting. As withpreliminary bench testing, the position of peaking was focussed on theindentation site.

Can ends modified in this way were also tested by pressurising a can towhich the end was seamed (“seamed end test”). These results are shown intable 2. Whilst the cans all peaked on the indentation site and werestill openable after peaking, only 25% survived testing without leakingon the peak location. TABLE 1 (Bruceton staircase test) Expandedcountersink bead Drop test (onto 30° sheet steel) PEAK ON HEIGHT LEAK ONCONTROL CAN (″) PEAK? FEATURE? PEAK TYPE 1 5 N Y P 2 10 N Y PS 3 5 N Y P4 10 N Y P 5 15 N Y PS 6 10 N Y PS 7 5 N Y P 8 6 N Y P 9 7 N Y P 10 8 NY PS 11 7 N Y P 12 8 N Y PS 13 7 N Y P 14 8 N Y PS 15 7 N Y P

TABLE 2 (SET test) PEAK ON PRESSURE CONTROL CAN (psi) SURVIVE? FEATURE?OPENABLE? 1 95 N Y Y 2 93.4 Y Y Y 3 99.3 N Y Y 4 100.4 N Y Y Average97.0 25% 100% 100%

-   P=standard peak with no leak-   PS=peaked and burst at the score

EXAMPLE 2

Further can ends were then modified in the conversion press both byexpanding the countersink bead over a 60° arc at positions +/−90° of thetab heel, and also by providing a indentation over a 50° arc atpositions +/−90° in the upper chuck wall. These ends were then seamedonto filled cans and drop tested by dropping vertically, tab end down,onto a steel plate, the sheet steel being inclined at 30°. The resultsof the second tests are given in table 3, where again P=standard peakand PS=peak and score burst.

The combination of a countersink bead expansion and indentation in thechuck wall increases the average height at which peaking occurs. Thecountersink bead expansion was found to act as a trigger and thiscombination of a trigger and chuck wall indentation controls the peakingbetter than a countersink bead expansion alone (example 1).

Can ends modified in this way were also tested by pressurising a can towhich the end was seamed (“seamed end test”). These results are shown intable 4.

In the results of table 4, all the cans again peaked on the indentationsite and were still openable after peaking. In addition, 100% survivedtesting without leaking on the peak location, supporting the Applicant'sdiscovery that by combining two types of control feature, performance interms of leak-free failure mode is dramatically improved. TABLE 3(Bruceton staircase test) Expanded countersink bead + chuck wall grooveDrop test (onto 30° sheet steel) ON HEIGHT LEAK ON CONTROL CAN (″) PEAK?FEATURE? PEAK TYPE 1 5 N Y P 2 10 N Y P 3 15 Y Y P 4 12 Y Y P 5 11 N Y P6 12 Y Y P 7 11 N Y P 8 12 Y Y P 9 11 N Y P 10 10 Y Y P 11 8 N Y PS 12 9Y Y P 13 8 N Y P 14 9 Y Y P 15 8 N Y P

TABLE 4 (SET test) PEAK ON PRESSURE CONTROL CAN (psi) SURVIVE? FEATURE?OPENABLE? 1 93.7 Y Y Y 2 87 Y Y Y 3 93.2 Y Y Y 4 92.3 Y Y Y Average 91.6100% 100% 100%

EXAMPLE 3

Can ends having an indentation in the upper chuck wall only (i.e. not inthe countersink) were seamed to can bodies and then pressurised. Runs 1to 8 had a single indentation behind the tab over an arc of about 40° to50°. Runs 1-1 to 8-8 had indentations at +/−90° and over a 50° arc. Meanresults are given throughout. Peak location indicates the incidence of apeak on the control feature. The spacer details explain the degree ofindentation in the chuck wall. TABLE 5 (SET test) Reversal % peak onRadial spacer Indent RUN pressure (psi) control feature SurvivalOpenable (mm) spacer 1 99.03 100% 25% 100% 0.5 8.75 2 101.7 75% 50% 100%0 8.75 3 92.48 100% 75% 75% 0 9.25 4 91.3 100% 25% 75% 0.5 9.25 5 101.83100% 75% 100% 0.5 10.75 6 103.2 100% 100% 100% 0 10.75 7 94.65 100% 50%100% 0 11.25 8 93.45 100% 75% 100% 0.5 11.25 1—1 101.45 100% 75% 75% 0.58.75 2—2 101.83 75% 75% 100% 0 8.75 3—3 92.35 100% 75% 100% 0 9.25 4—489.6 100% 25% 100% 0.5 9.25 5—5 102.0 100% 75% 100% 0.5 10.75 6—6 103.9575% 50% 100% 0 10.75 7—7 94.98 100% 75% 100% 0 11.25 8—8 95.8 100% 75%100% 0.5 11.25 CONTROL 105.98 N/A 25% 100% N/A N/A

EXAMPLE 4

Further trials were conducted to confirm the effect of expansion of thecountersink radius and the indentation in the upper chuck wall, bothseparately and together. Unmodified can ends were tested by way ofcontrol. The results are shown in tables 6 and 7.

The chuck wall indentations comprised a indentation on each side of thetab, set at 90° to the tab. Spacer conditions were as in example 3, butwith a 9 mm indent ring spacer (rather than 8.75 mm).

The countersink “trigger” comprised a single bead expansion within thearc of the chuck wall indentation and centred on the same diameter (arcmid-point). This bead expansion was selected to trigger a peak withinthe chuck wall indentation as identified in example 2.

The control can ends give very low survival figures in both drop testsand seamed end testing (SET), i.e. the control can ends leak when theypeak. The chuck wall indentation alone gives good hot drop (100° F.) andSET performance but seems to have higher incidence of score burstsduring hot drop testing. The countersink (“c′sk”) bead trigger creates avery symmetric end shape from the hot drop test and is very effective indetermining the peak location. The countersink trigger reduces the SETperformance to 89 psi average, but this is believed to be attributableto the tooling used to create the indentations. In general “1” means yesand “0” means no, except in position in which 1 indicates the positionof peak on the control feature. TABLE 6 (Bruceton staircase comparingunmodified with various modified can ends) Unmodified control Bothfeatures Leak C'sk bead trigger only Chuck wall only Leak Height Leak ?type Height Leak ? Position? Leak Type Height Leak ? Position? Leak TypeHeight Leak ? Position? Type 5 y p 5 Y 1 p × 2 5 n 0 p × 2 5 Y 1 clam-shell 4 y p 4 Y 1 p × 2 5 y 1 p 4 N 1 p × 2 3 y p 3 Y 1 p × 2 4 n 1 p 5Y 1 p × 2 2 y p 2 Y 1 p × 2 5 n 1 p 4 N 1 p × 2 1 y score 1 Y 1 scoreburst 6 n 1 p 5 N 1 p × 2 burst 1 n none 1 Y 1 score burst 7 y 1 scoreburst 6 Y 1 p × 2 1 n p 1 N 1 score burst 6 y 1 p × 2 5 N 1 p × 2 2 y p2 N 1 score burst 5 n 1 p × 2 6 N 1 p × 2 1 y p × 2 3 Y 1 p × 2 6 y 1 p× 2 7 Y 1 p × 2 1 y score 2 Y 1 p × 2 5 n 1 p 6 Y 1 p × 2 burst 1 y p 1Y 0 p × 2 6 n 1 p × 2 5 N 1 p × 2 1 n p 1 Y 1 score burst 7 n 1 p × 2 6N 1 p × 2 2 n p 1 N 1 p × 2 8 n 1 p 7 Y 1 p × 2 3 y p 2 Y 1 score burst9 n 1 score burst 6 Y 1 p × 2 2 n p × 2 1 N 0 p × 2 9 n 1 score burst 5N 1 p × 2 3 y p 1 N 1 score burst 9 y 1 p × 2 6 N 1 p × 2 2 y p 2 Y 1 p× 2 8 n 1 p × 2 7 N 1 p × 2 1 n none 1 Y 1 p × 1 9 y 1 score burst 8 N 1p × 2 2 n p 1 N 1 p × 1 8 n 1 p × 2 9 Y 1 p × 2 3 n p 2 Y 1 p × 1 9 n 1p × 2 8 Y 1 p × 2 4 y p × 2 1 Y 1 p × 1 10 y 1 p × 2 7 N 1 p × 2 3 n p 1Y 1 p × 1 9 n 1 p × 2 8 N 1 p × 2 4 n p 1 Y 1 score burst 11 n 1 p × 2 9Y 1 p × 2 5 y p 1 Y 1 score burst 12 n 1 p × 2 8 Y 1 p × 2 4 y p 1 Y 1score burst 13 n 1 p × 2 7 Y 1 clam- shell 3 y p 1 Y 1 score burst 14 n1 p × 2 6 Y 1 p × 2 2 y p × 2 1 Y 1 p × 2 15 n 1 p × 2 5 N 1 p × 2 1 y p× 2 1 Y 1 score burst 15 y 1 p × 2 6 Y 1 p × 2 1 n p 1 Y 1 score burst14 n 1 p × 2 5 N 1 p × 2 2 n p 93% 97% 100%

TABLE 7 (SET comparisons of unmodified with modified can ends) Can 1 Can2 Can 3 Can 4 Can 5 Can 6 Can 7 Can 8 Can 9 Can 10 Average UNMODIFIEDBUCKLE PRESSURE (psi) 103.4 101.1 99.7 101.6 104.4 102.9 98.3 97.9 98.3108 102 POSITION ? n/a n/a n/a n/a n/a n/a n/a n/a n/a n/a n/a SURVIVED? 1 0 0 0 0 0 0 0 0 1 20% OPENS ? 1 1 1 1 1 0 1 1 1 1 90% C'sk BEADTRIGGER DENT ONLY BUCKLE PRESSURE (psi) 88.4 91.9 92.5 91.7 91.2 91.491.1 92 95 92.7 92 POSITION? 1 1 1 1 1 1 1 1 1 1 100% SURVIVED ? 0 0 0 00 0 0 0 0 0 0% OPENS ? 1 1 1 1 1 1 1 1 1 1 100% CHUCK WALL DENT ONLYBUCKLE PRESSURE (psi) 96.6 95.7 92.7 93.7 94.3 94.6 92 95.1 93.7 95.5 94POSITION? 1 1 1 1 1 1 1 1 1 1 100% SURVIVED ? 1 1 1 1 1 1 1 0 1 1 90%OPENS ? 1 1 1 1 1 1 1 0 1 1 90% BOTH DENTS BUCKLE PRESSURE (psi) 86.690.5 87.7 87.6 88.5 92.7 90.3 86.3 87.5 89 POSITION? 1 1 1 1 1 1 1 1 1100% SURVIVED ? 1 1 1 1 1 1 1 1 1 100% OPENS ? 1 1 1 0 1 1 1 1 1 89%

EXAMPLE 5

Further seamed end tests were carried out on both unmodified can ends(“control samples”) and can ends having a 360° control feature in theform of a shelf in the outer wall of the countersink bead. Results ofthese trials are given in table 8. Buckle pressure performance was wellabove the 90 psi industry standard for all cans, both standard andmodified. Only 25% of the control samples survived testing withoutleaking, whereas 100% of the cans having a control feature(circumferential shelf in the countersink bead) passed the test withoutleaking.

The invention has been described above by way of example only andnumerous changes and/or permutations may be made within the scope of theinvention as filed. It should also be noted that the control features ofthe invention are particularly intended for use on beverage can endswhich are to be fixed to a can body and thereby subjected to internalpressure. Furthermore, the control features may be used on can endshaving any chuck wall angle whether conventional (less than 15°) orlarger, such as that of the '634 patent, i.e. 30° to 60°. TABLE 8Control Samples Shelf in Bead Buckle Buckle Pressure Pressure (psi)(psi) Leak 102.6 n 98.1 n 102.3 n 104.1 n 105.6 y 102.3 n 105.6 y 96.8 n101.5 n 103.4 n 101.7 y 103.5 n 102.5 y 104 n 104.6 y 103.5 n 107 n 99.8n 103.4 y 105 n 103.5 y 103.6 n 104.2 y 104.1 n 103.6 n 103.9 n 102.2 n104 n 103 n 102.2 n 103 y 103.1 n 103.5 y 105.5 n 105.1 y 104.5 n 102.8y 101.9 n 102.8 y 104.1 n 104.7 y 100.5 n 103.8 y 103.2 n 103.8 y 102.3n 105.9 y 101.9 n 104.5 y 105.7 n 103.3 y 105.6 n 103.3 y 98.6 n 104.5 y101.3 n

1. A can end shell comprising a center panel, a countersink bead, achuck wall portion, a seaming panel, and one or more control features,each control feature extending around an arc of at least part of thecountersink bead and/or the chuck wall, whereby the failure mode of thecan end, when seamed to a can body, is controlled, and in which the oreach control feature comprises one or more of: an expansion of thecountersink bead, a shelf in the outer wall of the countersink, anindentation in the chuck wall, and/or coining.
 2. An end shell accordingto claim 1, in which the control feature includes at least one featurewhich extends around the whole circumference of the end shell.
 3. An endshell according to claim 1, in which the control feature extends over anarc behind the heel of a tab fixed to the can end, and centered on adiameter through a tab central axis.
 4. An end shell according to claim1, in which a control feature is disposed on each side of a diameterthrough a tab central axis and each extending around an arc of the canend.
 5. An end shell according to claim 3, in which the arc length is90° or less.
 6. An end shell according to claim 1, in which said endshell includes a combination of different types of control featuresextending around an arc centered on the same diameter of the can end. 7.An end shell according to claim 1, in which each control featurecomprises at least an expansion of the countersink bead and anindentation in the chuck wall, extending around an arc centered on thesame can diameter.
 8. An end shell according to claim 7, in which thearc length of the bead expansion is less than the arc length of thechuck wall indentation, such that the bead expansion acts as a trigger.9. An end shell according to claim 1, in which an indentation or coinedregion is positioned at least partially in the upper half of the chuckwall, extending either internally or externally, or a combination ofthese.
 10. An end shell according to claim 1, further comprising coiningof a shoulder between the inner wall of the countersink and the centerpanel over an arc or pair of arcs.
 11. An end shell according to claim1, in which the control feature is made in either a shell press or aconversion press or a combination of these.
 12. An end shell accordingto claim 4, wherein the arc length is 90° or less.
 13. An end shellcapable of being double seamed to a can body, said end shell comprisinga center panel, a countersink bead disposed radially outwardly from thecenter panel, a wall portion disposed radially outwardly from thecountersink, a seaming panel disposed radially outwardly from the wallportion, and failure control means for controlling eversion of thecountersink bead.
 14. The end shell according to claim 13, in which thecountersink bead extends from the center panel.
 15. The end shellaccording to claim 14, in which the wall portion extends from thecountersink bead.
 16. The end shell according to claim 15, in which theseaming panel extends from the wall portion.
 17. The end shell accordingto claim 13, in which controlling eversion includes diminishing apropensity of the end to leak upon eversion of the counter sink bead.18. The end shell according to claim 17, in which controlling eversiondiminishes the strength of the end.
 19. A combination beverage can bodyand end seamed to said can body in a double seam, said end comprising acenter panel, a countersink bead disposed radially outwardly from thecenter panel, a wall part disposed radially outwardly from thecountersink, a seam disposed radially outwardly from the wall part, andfailure control means for controlling eversion of the countersink bead.20. The combination according to claim 19, in which the countersink beadextends from the center panel.
 21. The combination according to claim20, in which the wall part extends from the countersink bead.
 22. Thecombination according to claim 21, in which the seaming panel extendsfrom the wall part.
 23. The combination according to claim 19, in whichcontrolling eversion includes diminishing a propensity of the end toleak upon eversion of the counter sink bead.
 24. The combinationaccording to claim 23, in which controlling eversion diminishes thestrength of the end.
 25. An end shell capable of being double seamed toa can body, said end shell comprising a center panel, a countersink beaddisposed radially outwardly from the center panel, a wall portiondisposed radially outwardly from the countersink, a seaming paneldisposed radially outwardly from the wall portion, and a weakeningdeformation in the countersink bead, whereby said weakening deformationis capable of affecting eversion of the countersink to reduce leakingupon eversion.
 26. The end shell of claim 25, in which said weakeningdeformation is formed in a continuous circumference.
 27. The end shellof claim 25, in which said weakening deformation is formed in an arcuateregion less than 360 degrees.
 28. The end shell of claim 25, in whichsaid weakening deformation is substantially formed by pointindentations.
 29. The end shell of claim 25, in which said weakeningdeformation comprises an expansion of the countersink bead.
 30. The endshell of claim 25, in which said weakening deformation comprises a shelfin the outer wall of the countersink.
 31. The end shell of claim 26, inwhich said weakening deformation comprises a shelf in the outer wall ofthe countersink.
 32. The end shell of claim 25, in which said weakeningdeformation comprises coining.
 33. The end shell of claim 32, in whichsaid coining is disposed at least on an inside shoulder of saidcountersink.
 34. The end shell of claim 33, in which additional coiningis disposed at least on an outside shoulder of said countersink.
 35. Theend shell of claim 33, in which additional coining is disposed at leaston an outside shoulder of the wall portion.
 36. The end shell of claim26, in which said weakening deformation comprises coining.
 37. The endshell of claim 30, in which said weakening deformation comprisescoining.
 38. The end shell of claim 3 1, in which said weakeningdeformation comprises coining.
 39. The end shell of claim 25, in whichsaid can end further comprises another weakening deformation formed inthe end wall portion.
 40. The end shell of claim 26, in which said canend further comprises another weakening deformation formed in the endwall portion.
 41. The end shell of claim 30, in which said can endfurther comprises another weakening deformation formed in the end wallportion.
 42. The end shell of claim 31, in which said can end furthercomprises another weakening deformation formed in the end wall portion.43. The end shell of claim 32, in which said can end further comprisesanother weakening deformation formed in the end wall portion.
 44. Theend shell of claim 36, in which said can end further comprises anotherweakening deformation formed in the end wall portion.
 45. The end shellof claim 37, in which said can end further comprises another weakeningdeformation formed in the end wall portion.
 46. The end shell of claim38, in which said can end further comprises another weakeningdeformation formed in the end wall portion.
 47. The end shell of claim25, in which said weakening deformation triggers the eversion.
 48. Acombination beverage can body and end seamed to said can body in adouble seam, said end comprising a center panel, a countersink beaddisposed radially outwardly from the center panel, a wall part disposedradially outwardly from the countersink, a seaming panel disposedradially outwardly from the wall part, and a weakening deformation inthe countersink bead, said weakening deformation capable of affectingeversion of the countersink to reduce leaking upon eversion.
 49. Thecombination of claim 48, in which said weakening deformation is formedin a continuous circumference.
 50. The combination of claim 48, in whichsaid weakening deformation is formed in an arcuate region less than 360degrees.
 51. The combination of claim 48, in which said weakeningdeformation is substantially formed by point indentations.
 52. Thecombination of claim 48, in which said weakening deformation comprisesan expansion of the countersink bead.
 53. The combination of claim 48,in which said weakening deformation comprises a shelf in the outer wallof the countersink.
 54. The combination of claim 52, in which saidweakening deformation comprises a shelf in the outer wall of thecountersink.
 55. The combination of claim 48, in which said weakeningdeformation comprises coining.
 56. The combination of claim 55, in whichsaid coining is disposed at least on an inside shoulder of saidcountersink.
 57. The combination of claim 56, in which additionalcoining is disposed at least on an outside shoulder of said countersink.58. The combination of claim 56, in which additional coining is disposedat least on an outside shoulder of the wall part.
 59. The combination ofclaim 52, in which said weakening deformation comprises coining.
 60. Thecombination of claim 53, in which said weakening deformation comprisescoining.
 61. The combination of claim 54, in which said weakeningdeformation comprises coining.
 62. The combination of claim 48, in whichsaid can end further comprises another weakening deformation formed inthe end wall part.
 63. The combination of claim 52, in which said canend further comprises another weakening deformation formed in the endwall part.
 64. The combination of claim 53, in which said can endfurther comprises another weakening deformation formed in the end wallpart.
 65. The combination of claim 54, in which said can end furthercomprises another weakening deformation formed in the end wall part. 66.The combination of claim 55, in which said can end further comprisesanother weakening deformation formed in the end wall part.
 67. Thecombination of claim 59, in which said can end further comprises anotherweakening deformation formed in the end wall part.
 68. The combinationof claim 60, in which said can end further comprises another weakeningdeformation formed in the end wall part.
 69. The combination of claim61, in which said can end further comprises another weakeningdeformation formed in the end wall part.
 70. The combination of claim48, in which said weakening deformation triggers the eversion.
 71. Anend shell capable of being double seamed to a can body, said end shellcomprising a center panel, a countersink bead disposed radiallyoutwardly from the center panel, a wall portion disposed radiallyoutwardly from the countersink, a seaming panel disposed radiallyoutwardly from the wall portion, and a weakening deformation in the wallportion, whereby said weakening deformation is capable of affectingeversion of the countersink to reduce leaking upon eversion.
 72. The endshell of claim 71, in which said weakening deformation is formed in acontinuous circumference.
 73. The end shell of claim 71, in which saidweakening deformation is formed in an arcuate region less than 360degrees.
 74. The end shell of claim 71, in which said weakeningdeformation is substantially formed by point indentations.
 75. The endshell of claim 71, in which said weakening deformation comprises anindentation.
 76. The end shell of claim 71, in which said weakeningdeformation comprises coining.
 77. The end shell of claim 71, in whichsaid weakening deformation comprises a shelf.
 78. The end shell of claim71, in which said can end further comprises another weakeningdeformation formed in the countersink bead.
 79. The end shell of claim78, in which said can end further comprises coining disposed at least onan inside shoulder of the wall portion.
 80. The end shell of claim 78,in which said can end further comprises coining disposed at least on anoutside shoulder of the wall portion.
 81. The end shell of claim 71, inwhich said weakening deformation triggers the eversion.
 82. Acombination beverage can body and end seamed to said can body in adouble seam, said end comprising a center panel, a countersink beaddisposed radially outwardly from the center panel, a wall part disposedradially outwardly from the countersink, a seaming panel disposedradially outwardly from the wall part, and a weakening deformation inthe wall part, whereby said weakening deformation is capable ofaffecting eversion of the countersink to reduce leaking upon eversion.83. The end shell of claim 82, in which said weakening deformation isformed in a continuous circumference.
 84. The end shell of claim 82, inwhich said weakening deformation is formed in an arcuate region lessthan 360 degrees.
 85. The end shell of claim 82, in which said weakeningdeformation is substantially formed by point indentations.
 86. The endshell of claim 82, in which said weakening deformation comprises anindentation.
 87. The end shell of claim 82, in which said weakeningdeformation comprises coining.
 88. The end shell of claim 82, in whichsaid weakening deformation comprises a shelf.
 89. The end shell of claim82, in which said can end further comprises another weakeningdeformation formed in the countersink bead.
 90. The combination of claim89, in which said can end further comprises coining disposed at least onan inside shoulder of the wall part.
 91. The combination of claim 89, inwhich said can end further comprises coining disposed at least on anoutside shoulder of the wall part.
 92. The combination of claim 82, inwhich said weakening deformation triggers the eversion.